electrical gremlins are back

More info: when the key is OFF, I get 5v at the fuse box "hot buss" red w/ white stripe wire and at the welded splice. When i turn the key to ON, I get .1v at the same spots, and then .4v when the key is in ACC. Also, my temperature gauge immediately goes to H on the gauge when the key is on or off, it has always done this and is nothing new but I am trying to give as much info as possible.